Two-wire rotary-connector telephone system.



T. G. MARTIN. Two wlREVRoTARY CONNECTOR TELEPHONE SYSTEM.

T. G. MARTIN.

TWO WIRE ROTARY CONNECTOR TELEP HONE SYSTEM.

APPLICATION FILED ocT. II. 1909. IIEIIEwED JUNI: 1. 191s.

Patented J an. 2l, 1919'.

3 SHEETS-SHEET 2.

. T. G. MARTIN. TWO WIRE ROTARY CONNECTOR TELEPHONE SYSTEM. APPLICATIONFILED ocr. II| 1909. IIEIIEwED JuIII: 7, 191s.

Patented Jan. 21, 1919.

3 SHEETS-SHEET 3.

Aoffz' UNITED sTATEs PATENT OFFICE.'

TALBOT G. MARTIN, OF CHICAGO, ILLINOIS, ASSIGNOR TO AUTOMATIC ELCTRICCOMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

TWO-WIRE ROTARY-CONNECTOR TELEPHONE SYSTEM.

Specification of Letters Patent.

Patented Jan. 21, 1919.

Application led October-11. 1909, Serial No. 522.065. Renewed .Tune 7.1918. Serial No. 238.795. f

To all-whom z't may concern.'

Be it known that I, TALBOT G. MARTIN, a citizen of the United States 0fAmerica, and

resident of Chicago, Cook county, Illinois,

change systems in general, but more particu-` larly to automatic orsemi-automatic exchange systems, and especially to systems in whichprovision is made for controlling automatic switches, such as selectorsand connectors, over metallic line circuits.

For certain broader purposes of my invention the talking current may besupplied either from a common battery or from local batteries at thesubscribers7 stations. `Also, for the broader purposes of my'inventionthe first selectors may be employed on a percentage basis or asindividual switches for the subscribers lines. I have, however, electedto illustrate my invention in connection with that specific form'ofautomatic telephone exchange system in which common battery means anemployed for furnishing the talking'current. and in which the firstselectors are employed on a percentage basis. With this arrangement, aswill hereinafter more fully appear, means are provided for automaticallyselecting idle first selectors. In this way each calling= sub- Iscriberdoes two things before operating the first selector and other numericalswitches in :wcordalicc with the called number. First, the calling lineis automatically connected with a preselected idle trunk leading to anidle first selector; second, another idle trunk is selected for thesubscriber who makes the next call.l Thus each calling subscriberobtains connection with an idle first selector through the medium of apreselected trunk As herein disclosed, these switching operations areall lcontrolled by the calling subscriber over metallic line circuits.In other wordsyno operating grounds are ernployed at the substations ofthe system.y

'In the practice of automatic telephony it, has often been founddesirable to give a subscriber more. than onetclephone line, or

to providea plurality of trunk lines leading to a private branchexchange. In such case means are provided for automatically selecting anidle one of the said telephone lines, the same all being glven the samenumber, inasmuch as any one of these lines Will serve the purpose of thecalling subscriber.

'I his is also true where a number of trunk lines are provided for aprivate branch ex-A change, as in such case a calling subscriber issatisfied to obtain connection with any one of said trunk lines. Thesetrunk lines all have the same number, and if one or more of them arebusy it Will serve the purpose of any calling subscriber to obtainconnection with any one of the remaining idle trunk lines. For thisautomatic selection of an idle one of a number of telephone lines, or ofan idle trunk line, it has been the practice, to employ what areordinarily known as rotary connectors-that is to say, connectors whichare capable of rotating automatically in one or more or even all of thebank levels thereof, very much as a selector automatically rotates tofind an idle trunk line. There is, however, this difference between theautomatic selective operation of a rotary Vconnector and the similarautomatic selective operation of a selector.

In a selector the wipers are raised step by step to the desired levelunder the control of the calling subscriber. or of an operator.

When the wipers of the selector reach the predetermined level, they thenautomatically rotate in that level, without the necessity of any furtheract on the part of the calling subscriber. until an idlc trunk line isfound. In a rotary connector, however, the wipers thereof, when raisedtothe desired level` do not at once commence rotating inl that level,

but to the contrary remain opposite that particular level of bankcontacts until made to proceed in a rotary manner by some further act onthe part of the calling subscriber. For example. a selector isresponsive to the impulses for only one digit of the called number.These impulses raise, the wipers of the selector to thel desired level,and without the transmission of any further impulses llO that thesecontacts are arranged in levels, each level containing ten sets of bankcontaets, to each of which one line is allotted.

In this case it is assumed that the second level of the second selectorbanks are provided with trunks to rotary connector switches similar tothose shown in Fig. 2, while the trunks from the fourth level ter-Ininate in connector switches similar to those shown in Fig. 3. Trunksfrom the remaining levels terminate in connectors, as yshown in Fig. 3,but said connectors have no automatic rotary selective operations. 1

The substations may be of any suitable or approved type. As shown, itwill be seen thatv substation A is arranged to operate in connectionwith a two-wire system-that is, a system in which no ground connection-is used at the subscribers substation. Substation A, for example,comprises the usual receiver 2, switch hook 3, induction coil 44 whichconsists of the primary winding 5 and secondary winding 6, transmitter7, condenser '8,y ringer 9, and impulse wheel 10 which has the usualimpulse teeth 11. The impulse wheel 10 is secured to the shaft 12, toWhichshaft there is also secured the dial (not shown). vAs the dialreturns to normal position after being rotated to call a digit theimpulse teeth 11 are adapted to engage the cam 13 upon the end of thespring 14, and thereby ca'rry the latter out of engagement with thespring 15. Upon the switch hook 3 there is the cam arm 16 which, whenthe switch hook is up, permits the springs 17 and 18 to engage, therebybridgingacross the'subscribers line conductors 19 and 20 the primarycircuit including the transmitter 7 in series with the primary winding5; but when the switch hook is lowered the spring 17 is carried outofengagenient with thet spring 18 and into engagement with the spring18, whereby vthe ringer 9, in series with the condenser 8, is bridgedacross the line conductors 19 and `20 instead.

The line switch C may be of any suitable or approved type. For instance,it may be a modified form of the line switch disclosed in British PatentNo., 26,301 of 1906, and described in the American Telephone .lournal ofChicago, Illinois, of June 6, 1908.- In its'general form it comprises atrip magnet 23, a release magnet 24 and a bridgecut-ff relay 48; Thetrip magnet 23 is designed to operate the usual plunger for pressing thebank springs and 36, 37 and 38. 39 and 40, and 41 and 42 intoengagement.' This plunger is soarranged that when in normal position itis under the control of the master switch J, whereby the said plungermay always be removed from opposite busy-trunk to a position opposite anidle trunk. The release magnet operates to restore the plunger to normalposition.

switches, usually one hundred, always holdihe motor magnet isdenergized.

The bridge-cut-otf relay 48 operates to shift the springs 49 and 52 outof engagement with the springs 50 and 51, respectively.

The master switch I may be of any suitableor approved type. Forinstance, it may be a modified form of the master switch described andillustrated. in the said lmcrican Telephone Journal of June 6, 1908. Inits general form it comprises a motor magnet 53, a motor magnet relay56, the circuitopening relay 25, ratchet wheel 55, interrupter whepl 54,master switch bank Q, wiper 58 and condenser 27. The switch yshaftcontrols the plungers of several line ing them' in readinessto engage anidle trunk. Thls part1cular master switch 'shaft f has a step-by-stepreciprocating motion, and

all idle plungers are held in locking engagement with said shaft. Theplungers of the line switches, as described in the publicationmentioned, are not self-alining-that is, a plunger does notautomatically come into locked engagement with the shaft until themaster switch shaft again resumes the original position where theplunger was tripped. When one line switch operates, its plunger istripped and engages the springs of the bank terminals of an idle trunk.The motor magnet relay 56 is accordingly energized. This relay operatesto close the motor magnet circuit and the circuit of the relay 25. Themotor magnet operates to rotate the ratchet wheel and intcrruptcr wheel.When the ratchet wheel is rotated 100 one'notch the interrupter wheelhas'rotated enough to close the springs 21 and 22, which keep the motormagnet operating until the idle plungers are directly opposite the bankterminals of an idle trunk. lVhen this position is reached the springs21 and 22 separate, and as the master switch wiper 58 has been moved' toa position on the master switch bank corresponding to an idle trunk.

Thilo the motor magnet is operating, the circuitopening relay 25 isenergized. thereby shifting the spring 32 out of engagement with thespring' 33 and into engagement with the spring 34. In this way all thetrip magnets are disconnected from the battery lead and connected to thebusy-signaling current similar to the busy-signaling current furnishedby the apparatus I in Fig. 2, thus preventing thc selection of a busytrunk and giving a subscriber the busy-signal if all the trunks arebusy.

The first selector switch shown at D is an improved form of the selectordescribed in United States Letters Patent No. 815,321, granted March 13,1906, to Keith, Erickson andv Erickson, and is adapted to operate inconnection with a two-Wire system. Among other details it embodies thefollowing fea'- tures: The'switch shaftgtnot shown)- carries 130 thevertical and rotary 'Wipers 81- and 82,

rotary magnet wiper, respectively. The

.side switch is under the control of the private magnet 88, and when theside switch is in norma-l or first position the wipers 841, 85, 86 and87 occupy the contact points 89, 90, 91 and 92, respectively. ln thesecond position the 'wipers rest on the Contact points 93, 0l, and 96,respectively; and in third positionthe contact points 97, 98, 99 and 100are engaged by their respective wipers. The windings ofi the usualvertical and rotary line relays are, in this case, conii bined into onedouble wound relay 101 coniprising the winding 102 which is connectedwith the battery lead 103, and also with the vertical line trunkconductor when the side switch wiper 811 is in lirst or second posietion. The second winding 10st is connected to ground, and also to therotary line trunk conductorwhen the side switch wiper 85 is in first orsecond position. medium of this double wound relay, and while the sideswitch isin first position, the subscriber controls the yer-tical"magnet 105, which operates to raise the switch shaft and wipers S1, 82and S3 vertically. This line relay 101 also controls the private magnetrelay 106,Which latter in turn controls the private magnet 88. r1`heprivate magnet, as

usual, controls the side switch. `While the side switch is in secondposition the rotary magnet 107, which operates to carry the switch shaftand wipers 81, 82 and S23 in a rotary direction, is energized. 'lherelease magnet 108 provides ineens for restoring the selector switch tonorinal position. .Upon the switch shaft, which carries the wipers 81,82 and 8S, there is mounted the arm 109 which., when the shaft is raisedone or incre steps, permits the soring 110 to engage the contact point111, wherehythe release inagnet 108 is connected to the battery. Therelease relay 112 provided for closing the energizing circuit of therelease magnet 108 after the switch is operated. The hackA` releaserelay 113 is provided or opening),A the energizing circuit through therelease inamet 2-1 of the line switch. The relai's 106, 112 andk 113 areslow-acting,l relaysthat is, they are so provided with a copper shieldthat when energized, and the energizing circuit then broken, the saidrelays remain for a moment in an operated position. ln other words, theydo not instantly return to normal position after the ener. ,ing circuitis breiten. Y

Theseeond selector lli is similar to the first selector l), and isprovided with the lrenal double-wound line relay 114s hailing;

Through the vselector switch.

asettico the windings 115 and 11G connected with the vertical and rotaryside switch Wipers 117 and `118 in the saine manner in which thewindings of the relay 101 of the selector switch D are connected. 'totheir vertical and rotary side switch wipers.

Since like parts are similarly represented, the rotary magnet 119 andVertical magnet 120 will he recognized and understood. The releasemagnet 121 is operated in the saine manner in connection with the svitch.l that the release magnet 108 is operated in lhe private connectionwith the switch l). magnet is controlled hy the privato niag net relay123. The release rel ay 124i out the second selector switch if) performsthe sanie function in connection with this switch as the release relay112 and the rhaelt-release relay 113 perform in connection with thefirst selector switch `1)-that is, the springs controlled hy the relays112 and 113 are so arranged in the second selector switch E that theyare controlled hy a central relay 1211. ln the switch E the relays 123and 124i. are so arranged that they denergize slowly, thc same as therelays 106, 112 and 113 oit the selector switch D.

The rotary connector switch li an imV proved forni of the connectorswitch disclosed .in United States Letters latent No. 815,176, grantedMerch 1?, 1906, to Keith, Erickson da ldlriel-son. in this rotaryconnector F means are provided whereby the shattniay he automaticallyrotated, like the shaft of the selector switches, when the privatewiperengages a lousy Contact, and also whereby it is adapted to operate inconnection with a two-wire coniinon battery system. The connector switchshait (not shown), like the shaft of the selector, carries the linewipers 125 and 126 and the private Wiper 12T. The connecter switch isalso controlled by the calling subscriber through the medim um 'of' adouble-wound line voley .lhe line relay 128 is provided with thewindings 129 and 130. @ne terminal otl the winding 129 is connected to'the battery lead, while the other terminal is connected with therertical trunk line conductor 192. The windn ing 12E-0 is connected withground and also with the rotary trnnl; line conductor llhis line relaydirectly controls the 'rertical magnet 1551, rl'he purpose of thevertical magnet 131 is to gite the shaft and shaft wipers a .ertiealmotion, and the rotary magnet 132 imparts to the shaft and shaft wipersa rotaryor circular motion. The connector switch is also provided withthe slow-actinggl release relay 15.3, which is similar to the releaserelay 1211 of the rllhe pr' iet r l y as usual, controls the p whichlatter. onder eert ,in conditions, con trois the rotary inegnct 132 andcleo the side switch Wipers 136, 137, 138, 139 and 140. The privatemagnet 135, as arranged to operate in connector switch E, plays a veryimportant part, and controls therotary action to a great extent. Theob]ect 1n providing the connector with this automatic seactive featureis as follows: Abusiness house r private branch exchange, for example,iay be providedhwith three lines,all of which are given the sainenumber; and it ,nay become desirable to so arrange the system that ifone line is in use, the calling switch will automatically extend thecalling subscribers line into connection with the second line; if thesecond line is also busy connection may be carried to a third line, andso on.A The calling subscriber would, of course, have no control overthe apparatus as to which one of the lines he makes connection with.rIIhis, however, does not concern him, since any trunk line to the saidoiice or private branch exchange will serve his purpose. The arrangementof the connector banks themselves will be as follows: If the oiiic'e atwhich the number 2221 is located wishes three telephones it will begiven three lines, one terminating in the irst contact of the secondlevel of the connector banks, and the second in the second contact ofthe second level. etc. Now, if the number 2221 is called, the connectoris raised' to the second level and then rotated into engagement with thetrsteontact of the second level; but if the said contact is busy theconnector is automatically rotated onto the second set of contacts. Itbecomes desirable, of course, to provide means for notifying the callingsubscriber in the event that all the -trunk lines are busy. Forv thispurpose a fourth set of bank contacts of the second level are connectedwith a busy-signaling circuit, at which contacts the connector' muststop in the event that all lines are busy. A busy-signaling current isthen sent to the calling subscribers line over a,circuit including thisfourth set of contacts of this level.- This arrangement, however, is notconiined to any particular level, as any level may be divided in thesameway, and any subscriber may thus be given any number of lines,depending on the number of contacts in each level. The back-bridge relay141, comprising the windings 142 and 143, provides means. whereby thecalled slibscriber is provided with battery current for talkingpurposes. Ashere shown, the connector switch has provision .forautomaticl ringing-that is, the signaling of the called subscriber isnot dlependent upon the calling subscriber-.pressing a signaling button,but as soon as connection is estz'lblishedwith the desired line theinterrupter 144 intermittently closes an energizing circuit through theringer relay 145, whereby the terminals of the ringer generator H areintermittently bridged across the normal conductors of the called line.The relay 146 is arranged in the private wiper circuit, and when thesaid'wiper engages the busy contact an energizing circuit is closedthrough this relay 146, which operates to close an energizing circuitthrough the private magnet 135. The means ,whereby the connector switchmay be restored to normal position consists of the usual release magnet133HL which, when the connector switch shaft is raised one or moresteps,is connected to the battery lead through the normal springs 131a and1321. By means of the condensers 147 and 148 the circuit through theconncf tor switch is divided into two sections. IThe busy-signalingapparatus I comprises the interruptor 149 in series with the winding 150of the inductioncoil 151. The inding 152 is connected with the spring 13,' and when the relay 154 energizes, as will be explained, thebusy-signaling apparatus 'is connected with the connector switch wiper126.

The connector switch L shown in Fig. 3 combines the automatic rotaryfeature of the connector F'with the ordinary features of asimpleconnector. The connector L is so arranged that if the wipers arebroughtinto engagement with a busy line on certain levels, said wipersremain on the terminals of that line, the side switch becomes locked insecond position to prevent the calling line from being extended intoconnection with the busy line, and the calling subscriber is given thebusy-signal.l If, however, the wipers arc brought into contact with abusy line on certain other levels, the said wipers are thenautomatically rotated onto an idle line in a manner` similar to that ofthe connector F. On to vof the frame of the connector is mounte( a groupof springs (292, 294, 291, 293 and 295) which is adapted to be operatedby the arm 289 which is attachcd to the top of the switch shaft. As vlong as these springs are in normal' posi- -tion-'that is, with thespring 293 in contact after the shaft has been raised high enough toforce' the springs 293 and 292 into the position shown in Fig. 4 theconnector then' operates like a rotary connector. By changing l(helength of the bushing on the end of the spring 293 the connector L maybe made rotary on as many levels as desired. For example, if it isdesired to provide two rotaryl levels the bushin on the spring 293 maybe made of such ength as to be engaged by the arm289 only after theshaft wipers are raised above the eighth level. Each of the bank levelsthat is engaged bv the wipers before the springs 292 and 293 areoperated can accommodater ten single subscrihers` while each level whichis engaged by the wipers after-said springs are operated 'canaccommbdate' one or more groups of lines7 all the lines of each groupbeing accessible by calling one number. This division of bank contactsinto groups is the saine as explained for the connector l?, the last conliacts of each group beingd connected to the busvsigualing machine l.rilhe connector L is also provided with a relay 278 for the purpose ofconnectingI the ground interrupter 279 with the rotary magnet 269 undercertain conditions, as will hereinafter appear. V

The ope'rationAoi the system may be more lclear-ly dis'closetrii.Ecachet-en, during the process "ot a call, is followed up in detail. 1twill be assumed that the substation i Wishes to call the otiice which isregistered as 2221 and which is provided with the substation A and A3,of which only substation A is shown.

To'call the number 2221 (substation A, Fig. 2) the subscriber atsubstation A (Fig. l) removes his` receiver` from the switch hook andoperates the calling device for each digit of the called number, in theWell-imown nrannerwthat is, when the receiver is re moved from theswitch hook a preliminary impulse provides an energizing circuit for thetrip magnet 23 of the line switch.v C, Wherebg7 the line switchA C isoperated to seize an `dle trunk line leading to a first selector switch.The dial is turned for the first digit, and upon returning to normalposition operates the first selector switch to establish connection withan idle trunk line y leading to a second selector switch. in a similarmanner the dial,` upon returning to normal position tor the seconddigit, operates the second selector switch E to establish Vconnectionwith an idle trunk line leading to a connector switch. The impulsesdelivcred`by the dial for the last two digits are directed toward the'connector F, which opcrates to place the shaft Wipers in lconnraftionwith the contacts corresponding to the desired oiiice. The preliminaryimpulse for energizing the trip magnet 23 occurs when the receiver 2 isremoved. from the switch hook, 3, and the cam arm 16 permits the spring17 to engage the spring 18, therebyY removingF the ringer from acrossthe line and bridging the primary circuit instead. Vvhen the primarycircuit is thus bridged across the line, the 'energizing circuit for thetrip magnet 23 is `completed and extends from ground G through thesprings 50 and' `lqmrotary line conductor 20, through the springs 17 and18, impulse springs 15 and 14, primary Winding 5, transmitter to thevertical line conductor 19, springs 52 and 51, through the ivmdlng ofthe trip magnet 23, springs 32 and 33 of the clrcuit--opening` ren lav2o to the battery lead 15'?, thence through lN-tr" Bt i n abili )at elyo gi oun its lsoon as t e tup magnet v23 energiaes, the piunger arm is'tripped and the plunger' engages the bank terminai springs et an idietrunk, as preiracheno viously described. `When the bank contacts arethus closed, the line conductors 19 and 20 are cut through to the trunkline conductors and 7d, whereby the line relay 101 of the selector Disenergized. This circuit extends from ground G5 through the Winding10ste?? (he double-wound line relayY 101, contact point 90, side ,switchWiper S5, trunk line.- conductor 7G, springs 38 and 37, line coin ductor20, primary circuit of substation fr, line conductor 19, springs 35 and36, truid line conductor 75, side switch Wiper 8e, con tact point 89,winding 102 et the relay 101 to the battery lead 157, thence through ba'tory B to ground G. The line relay 101 upon energizing operates todisengage the springl 161 from the spring-166 and to place it in contactwith the spring 162. The former action clears the release trunk 77 ofthe ground GG, which prevents the release magnetV 21 of the line switchJfrom energizing; the latter action establishes an energizing circuitthroughthe release relay 112, said ycircuit extending from ground G6through springiiA and into engagement with the spring 165. This is thecondition of the tiret selector D when the subscriber operates the dialfor the first digit. Furthermore, when the bank springs 39 and 40are'closed in eontact, after the line switch plunger-trips,thelbridge-cutoff relay L18 is energized over a circuit extending' fromground Gr through said bank springs, hridgecut-olf relay 48 to thebattery lead. The relay operates, fore innl the springs 49 and 52 out ofengagement with the springs 50 and 5l, clearingthe line conductors ofthe line switch circuits. The engagement of the bank springs 39 and il)also provides a guarding potential over the private normal conductor 80to the connector bank terminals corresponding to the line of the callingsubscriber to prewnt another subscribed from callingthe said line afterthe c'allingsubscriber at' substation A yremoves his receiverpreparatory to making' a call. VJhen the bank springs 4:1 and i2 areclosed in contact an energizing circuit is esl'alilishcd through themotor magnet relay :36 et the master switch J., it being undersl'oodthatthe ground connection G to the release trunk 77 at the selector D isremoved almost instantaneously. Said energizing circuit extends fromground G2 through the motor magnet relay 56, common segment 57 of themaster switch bank Q, Wiper 58, individual segment (50, bank springs 42and 41, release magnet 24 to the bittteryiead 15'1f thence throughbattery B to ground G. li' will be seen that the motor magnet relayv andrelease magnet 211- .are both included in this circuit; bnt the den ofcurrent is not sufficient to operate the magnet while the relay isoperated, closing the motor magnet kcircuit'and the circuit of thecircuit-openthrough thecircuit-openine relay 25, interrupter springs 70and'71, re ay springs 72 and 73 to the battery ltlad.l The relay 25 isslowacting-that is, slow to denergize, and thus remains in anopcratcdicondition while the motor magnet is operating, the intcrruptcr.springsvg70` andi-,71 being intermittently opened; The"circuit-openingrelay`when -operatcd' disconnects the lbattery lead from allA tripmagnets in the group,"thus making it'impossible for a trip nii'agnet torelease a .plungerwhile the c-1rcu1t of the motor magnet and relay 25Iis closed. The circuitopening relay 25 when operated also shifts thelspring 32 into engagement with the spring 31, thus connecting the tripmagnets to al source of busyfsignalingcurrent. The motor magnet operatesas a buzzer by means` ot the springs`70 and 71, successively energizing;and denergizing, to advmice the ratchetl wheel 55 and the'interrupterwheel 54. which in turn advance theshaft and all idle plungers that arein lockipg engagement with the shaft to a position opposite the nextidle bank terminal. As soon asthc motor magnet advances the ratchetwheel one step, the auxiliary springs 21 and Q2 'close in contact.thereby establishing the energizing circuit of the motor magnet 53'audthe relay 25 independently of the motor magnet relay 56. lVhen the wiper58 leaves the individual contact 60, ii' the next individual contact isnot guai'ded by a battery potential. the motor 'relay 56 will bedeiincrgizcd. However. theI motor magnet will continue to rotate t-heratchet wheel until the idle plungcrs are in a position directly introut ot the waiting idle trunk. This is accomplished by the springsQ1and` 2 (which are arranged in multiple with the springs 72 `and 73)making contact until toi-ced apart by the interrupter cam wheel 5.4. Itwill be seen that to give this condition the interruptor wheel 5l mustbe set in a position to operate these springs Q1 and 22 according to therelative `position of the idlc plungers. lt will be understood. otcourse. that the line switch bank terminal shown corresponds to thefirst segment of the master switch bank Q. and therefore corresponds-tothe trunk line conductors 75, 76 and 77 which terminate in the selectorD. The master switchwill accordingly come to rest in a position wherethe plungers are directly in front of an idle trunk terminal.

y The first digit being 2. the impulse spring 14 is twice carried out ofengagement with Ainto engagement with the first contact of the impulsespring 15. As a result the encrgizing circuit through the line relay101.is broken twice, and the spring 161 comes into contact with theyspring 166 twice. After the two impulses are thus delivered the liucrelay 101 again energizes and carries the spring 161 into contact withthe spring 162. As previously explained, the relay 112 is a slow-actingrelay-that is, slow to delinergize; and when this energizing circuit ismomentarily broken duririg the vertical im pulses just delivered, thesaid relay does not denergize, but remains in an operated posi.- tionrwith the spring 163 in contact with the spring 165. Then when thespring 161 engages the spring 166 two impulses are transmitted to thevertical magnet 105.

the springs 161 and 166 to the springs 163 and 165, through the privatemagnet relay 106. through the winding of the vertical magnet 105,contact point 92. side switch wiper 87 to the battery lead 157. thencethrough battery B to ground G. Two impulses being delivered, thevertical magnet 1 05 is thereby energized twice. and the shaft wipersare given two vertical steps in the .well known manner. It. will be seenthat the private magnet relay 106 is included in the energizing circuitot the vertical magnet 105. l This relay also energizcs. but being aslow-acting relay, it energizes on the rst impulse and remains so untilall the inipulses are transmitted. This relay. upon energizing. operatesto close thc. springs 167 and 168 in contact. whereby an energizingcircuit is established'through the private magnet4 88. This circuitextends troni ground G through the springs 167 and 168, private magnet88l to the battery lead 157, thence through battery B to ground G. Theprivate magnet relay 106 deiuergize-s after the last-vertical impulse,since this'energizing circuit is no longer maintained after the springs161 and 166 disengage. Hence. the said relay denergizes. permitting thcsprings 167 and 168 to disengage. whereby the energizing circuit throughthe private magnet 88 is in turn broken. which private magnet nowdeiinerv gizes and permits the side switch to pass from first to secondposition. permitting the side switch wipers S6 and l87 to engage thecontact points and 96. respectively. The closure of contact between theside switch wiper 87 and the contact point 96 sets up an energizingcircuit for the rotary magnet 107 vfrom ground G5 through theinterruptor rotary magnet then operates to rotate HB shaft wipers 81. 82and 83 of the selector f second position.

the second level oi the selector banks, from vwhich contact it isassumedthe trunk line conductors 170, 171 and 172 lead to the secondselector switch E. lr' the first trunk i is busy, however, and thewipers have to pass over busy contacts, then as soon as the privatewiper S3 engages the first private hunk contact, the private .magnet 88again energizes, locking' the side switch in The energizing` circuit'for said private magnet extends from vthe grounded terminal G of theybattery B through the switch of the busy trunk, through the privateWiper 83, thence through 'the conductor 173 to the side switch Wiper536, Contact point 95, through theV winding' of the private magnet tothe battery lead 157, thence through. battery B to ,Q'round G. Theprivate magnet S8, upon thus becoming energized, locks the side switchwiper 87 in engagement 'with the contact point 96, whereby the rotarymagnet 107 will be energized step hy step until the wipers are carriedonto the first idle trunk line. At the .instant that the private wiperleaves the last husy contact point the energizingu circuit through theprivate magnet S8 is destroyed.

and, a result the selector si deswitch passes to third position. 1f,however, there are no lousy trunkA lines the-*private magnet 88 releasesthe side switch to third position, in the weil known manner, as soon asthe wipers are carried into engagement with the first trunk line. Assoon as the side switch passes to third position, iis-stated, thesubscribers line conductors 19 and 2O are' exf circuit was establishedthrough the line revlay 101 or' the selector D when the subscribers lineconductors 19 and 20 were eX- tended through the line switch bank to thetrunk conductors 75 and 76. The relay 114, upon energizing, operates toshift the spring' li'from the spring 175 to the spring 176. I

W'hen the springs `174 and 176 engage, an erre'rgiziru'gv circuit isestablished through the release relay 124. This circuit extends fromAujrourui if?? through the springs 17 1 and 176, through the relay 124,to the battery lead 157, thence through battery .ll to ground G.

Vllhe relay, upon energizing, operates to shiftv the spring;r 177 'fromthe spring- 178 to the i spring 179, and the springs 180 and 181 arealsoclosed 'in contact.. This operation of the second selector switchloccurs at the 'instant that the side switch Wipers 841 and .tacts (notshown) naeneee 85 of the selector switch D pass to third position andextend the subscrihers line conductors 19 and 20 to the second selectorswitch E. When the second selector' switch therefore thus operates, aguarding potential is established at the private multiple contacts foriroteeting the seized trunk line conductors 110 and 171 against seizureley another calling first selector. This guarding potential extends fromground Gr8 to the Contact point 182, side switch Wiper 188, through thesprings 181 and 180, conductor 172 to the contact engaged by the privatewiper 83, and to the private multiple eon- Furthermore, when the firstselector switch D operates, and the side switch passes tothird position,anew ener- ,sizing circuit is established through the release relay 112.This energizing circuit extends rom ground GS at the selector switch Ethrough the springs 181 and 180, con ductor 172, shaft wiper 83,conductorrl, through the side switch wiper 86, Contact point 99 and therelay 112 to the battery lead 157, thence through battery 'B to groundGr. The relay 112 thus remains in an operated position with the spring163 in engagement with ythe spring 165, but the line relay 101 returnsto normal position when the side switch wipers Se and 85 en` gage thecontact points 97 and 98, respectively. The energizing' circuit throughthe line ,relay 114: extends from ground G through the winding 116 tothe-side switch wiper 118, thence through the conductors 171 and 76 andline conductor 20, throughr the primary circuit of the substation,through the verticalline conductor 19, thence through the trunkconductors 75 and 170, side switch wiper 117 through the Winding 115 ofthe relay 114 to `the battery lead 157, thence through battery B toground Gf. "When the dial returns te normal position for the seconddigit 2 this circuitthrough the line relay 114 is interrupted twice,when the impulse spring 111 is carried out of engagement with the spring15 by the impulse teeth on the wheel 19. The circuit'being interruptedtwice, the said relay 114 mo mentarily7 denergizes, thus permitting' theby an energizing circuit is completed through the vertical magnet 120,extending from ground G7 to the springs 174 and 175, springs 177 and179, through the winding of the private magnet relay 123, throughthewinding of the vertical magnet 120, con'- tact point 184C, sideswitch wiper 185 to the battery lead 157, and through battery B 'toground G. The private magnet relay 1231,

`spring 17a to engage the spring 175, Wherel heilig included in thiscircuit, energizesgand since it is a slow-acting" relayit remains in anoperated position until the last vertical impulse is delivered. vAfterthe two. iinpuises are thus deiivered, `the relay 111 l'with the spring201, and thc again energizes and carries the spring 174 into contactwith the spring 176, whereby the circuit through the private magnetrelay and the vertical magnet 120 remains open. When the relay123energizes, the springs 186 and 187 arepressed into contact, therebycausing an energizing current to flow through the private magnet 122,said circuit extending from ground G7, through the springs 187 and 186,through the winding of the private magnet 122 to the battery lead 157,thence'through battery B to ground G. lVhen the relay 123 denergizes andbreaks the energizing circuit through the pri 'ate magnet 122, theprivate magnet also -denergizes and permits the side switch to pass fromfirst to second position. When the side switch wiper 185 passes tosecond position and into engagement with the contactpoint 188, anenergizing circuit is established'through the rotary magnet 119 whichnow operates, as explained in connection with the rotary magnet 107 ofthe selector switch D, to select an idle trunk line leading to theconnector switch F. After the switch coines to rest with the side switchin third position, the shaft wipers 189, 190 and 191 are in engagementwith the trunk conductors 192, 193 and 194, respectively, which lead tothe connector switch F (Fig. 2). At the instant that the wipers 117 and118 pass to third position and into engagement with the contact points195 and 196", the subscribers line' conductors are extended to theconnector switch F, and an energizing circuit is established through theline relay 128 in the saine manner in which the energizing circuit wasestablished through the line relay 11-1` of the selectoi switch E whenthe side switch wipers ot' the first selector passed to third position.They energizing circuit through the line relay 128 extends from groundGW through the winding 130, trunk conductors 193, 171 and 76 to the lineconductor 20, thence through thc sub-station to the vertical lineconductor 19, trunk conductors 75, 170 and 192, thence through thewinding 129 to thc battery lead 157, and through battery B to ground (l.The line relay 128. upon energizing, operates to shift the spring 196from the spring 197 to the spring 198, whereby an energizing circuit isestablished through the rcleasc rclay 133 extending from ground (irlthrough the springs 196 and 19S, relay 135% to the battery lead 157,thence through battery B to ground .(1. 'hcn the relay 321 encrgizcs,the spring 199 is shifted out of engagement with thc spring 200 and intoengagement spring 202 is shifted into engagement with the spring 209.This primary operation of the connector relays 12S and 1321 occuis atthe instant that the side switch wipers 117 and 11S ot' the selector Epass to third position and extend side switch potential for protectingthe trunk line con-y ductors 192 and 193 against seizure byanothersecond selector. This potential extends fioni ground (i12 to thcsideswitch wiper 139, springs 203 and 202, conductor 191 to the privatebank contact engaged by the private wiper 191, and to the privatemultiple contacts (not shown). Furthermore, when the side switch ctv-thesecond. selector E passes to third position a new en,- ergizing circuitis established through the release relay 124, said circuit extendingfrom ground G12 at the connector switch to the conductor 194, throughthe shaft wiper 191, side switch wiper 20-1, contact point 205, throughthe release relay 124 to the battery lead 157, thence through battery Bto ground G. Also, this saine guarding potential established at thecontact engaged by vwiper 191, side switch wiper 201, contact point 205,contact' point 206, si'dc switch wiper 183, springsl 181 and 180,conductor 172 to the multiple private bank conta'ets of the irstselector switches. The cnengizing circuit of the release relay 112 f thcselector D is also extended to the connector F;

, this circuit, like the one last traced, extends to the conductor 172,thence through thc private wiper 83, conductor 173, side switch wiperS6, contact point 99, relay-112 to the battery lead 157. 'The opeijationof the dial for the last two digits affects the connector switch, andwhen thc dial is operated for thc third digit 2 thc impulse spring1-1vis twice carried out of engagement with thc spring 15, therebymomentarily 'dcenelgizing the line relay 12h twice, whereby the spring196 twice engages the'spring 19.7` thus sending two impulses to thevertical i'nagnct 131 troni ground (1, through the springs 196 and 197,springs 199 and 291, through the vertical magnet 1211...(-oiitact point207. side-switch wiper 1-10 o thc battcry lead 157. thence throughbattery l 'to ground (i. 'l'hc vertical magnet. upon lcing energized.operates` one slcp at a time to carry the shaft. wipers 125. 126 and 127two steps to a point oppositil the second lcvcl.

'hcn the liuc relay 12hl thus operates. an

the spring conductor 208, through the private magnet rela 134 to thebattery lead 157, thence through battery B to ground G. The relayv 13.4energizes and Ashifts `the spring 209 out of engagement with the spring210 'and into engagementv wit-li the spring 211; also, the spring 212 isshifted into engagement with 213. When the springs 212 and 213 engage,an energizing circuit is established through the private magnet 135 fromgroundGr13 through the springs213 and 212, private magnet 135 to thebattery lead 157, thence through battery B to ground G. The relay 134',being a slow acting relay, remains iii an operated position while theverticalA V impulses arebeing sent; but after all the impulses aredelivered, and. the line relay 128 returns to `its operated position,the circuit through the relay 134 becomes broken, thus permitting thesprings 212 and 209 to return to normal position.

` springs 212 and 213 disengage, the. circuit through the private magnet135 becomes broken, whereby the said magnet denergizes, permitting theside switch toV pass .from first to second position. The callingsubscriber now operates the dial for the last digitI 1, and again theline relay 128 is deenergized; but when the spring 196 engages thespring 197, an energizing circuit is established through'the `rotarymagnet 132 instead of through the vertical magnet 131.

This circuit extends fromr ground G11 through the springs 196 and 197,springs 199 and 201, conductor 208, springs 214 and 215, through thewinding of the rotary magnet 132, contact point 216, side switch wiper140 to the battery lead 157, thence through battery B to ground G. r1`herotary magnet. upon energizing operates to give the shaft and shat'twipers 125, 126 and 127 one rotary step, and to carry said wipersintoengageinent with the first bank contact of the second level, fromwhich contact the normal conductors 217 and 218 extend to a trunk lineleading lto the desired oitice. Also. when the line relay 128"denergized for the last digit, and placed lthe springs 196 and 197 inContact, an energizing circuit was established through the privatemagnet relay 134ias before. The relay 134, upon energizing, again closesthe circuit through the private magnet 135 when the springs 212 and 213engage, and when the relay returns to its energized position the circuitthrough the private magnet relay 134 vis again broken, and the1 circuitthrough the p'rivate magnet 135 is in turn also broken it' the firsttrunk line is idle. The side switch, therefore, passes from second tothird position. lhen the side switch wiper 4 vcalled subscriber.

ringer generator H across the lineV of the The energizing circuitthroughthe ringer relay 145 extends from ground G1* through theinterrupter 144, springs 220 and 221,-ringer relay 145, contact point219, side switch-wiper 140 to the battery lead 157, thence throughbattery f B to ground Gr. iVhen the connector side switch passes tothird position, and the side switch wiper 138 engages the groundedcontact point 222, a guarding potential is established at the connectorprivate bank to protect the 'seized line against interference by othercalling subscribers. This potential eX- tends -from ground G15 to thecontact point 222, side switch wiper 138, to the shaft private wiper 127which engages the private contact of the called line, and to themultiple private contacts of the. called line. Also, when the sideswitch wiper 138l engages the grounded contact point 222, an energizingcircuitis established through the cut-ofi1 relay ot the line switch C.This circuit extends from ground G15 through'the side switch wiper 138to the shaft private Wiper 127, conductor 224, through the Winding ofthe cut-,off relay 223 to the battery lead 157,

f thence through battery B to ground G. |The ringer relay 145, beingintern'iittently energized by the intei'i'upter 144, signaling currentis intermittently sent to the called substation A" from the ringerygenerator H through the springs 225 and 226, side switch wiper 136,contact point 227 shaft wiper 125, normal conductor 217, lineconductor-228, ringer 229 and condenser 230, through the springs 231 andto the line conductor 233, normal conductor 218, shaft wiper 126,contact point 234, side switch wiper 137, and through the ringer relaysprings 235'and 236 back to the ringer generator H. In response to thesignal the called subscriber removes the rcceiver 237 from the switchhook 238, whereby the spring 232 engages the spring 239, thus bridgingthe primary circuit, including the transmitter 240 in series with theprimary winding 241, across theline conductors 228 and 233. lVhen theprimary circuit comes across the line an energizing circuit isestablished through the relay 141 of the connector F, said circuitextending from ground (irla to the side switch wiper 138, winding 143 ofthe relay 141, thence through the ringer relay springs 242 and sideswitch wiper 137, contact pointI 234, shaft wiper 126. conductors 218and 233, springs 232 and 239, impulse springs 243. primary winding 241,transmitter 240, through the conductors and 217, shaft wiper 125, sideswitch wiper 136, ringer. relay springs 226 and 244, winding 142 of therelay 141 to the battery ,lead 157, thence through battery B to groundG. The relay 141 thereupon energizes and separates the i Switchsprings220 'and 221, whereby the intermittent circuit through the ringerrelay 145 becomes permanently broken.` The two substations A and Aare-now connected over ythe circuits shown by the heavy line conductorsin Figs. 1 and 2, the substation A receiving battery current for talkingpurposes through theline relay 128, while the substation i receivescurrent for talking purposes through the relay 141. In the preceding itwas assumed that the first trunk line, of which there are several,leading to the desired otlice was not busv. It will now be pointed outhow the connector switch F operates, it the first trunk line is busy, toautomatically select the first idle trunk line.

-when the rotary magnet 132 operates fol' Vthe last digit l, the privateshaft wiper 12'( comes into engagement with the first bank contact,which, it will be assumed, is protected by a guarding potential. In thatevent an energizing circuit is established through the private wiperrelay 146. This Circuit extends from the grounded terminal G of thebattery B through an occupying (not shown), through the bank con- Dtact,through the shaft Wiper 127, side switch wiper 138, contact point 246(the side switch being in second position), through the winding of theprivate wiper relay 146 to the battery lead 157, thence through batteryB to ground G. The relay 146 thereupon energizes and presses the springs247 and 248 into contact, closing an energizing circuit through theprivate magnet 135, said circuit extending from ground Gr16 through thesprings 247 and 24S, through the private magnet 135 to the battery lead,thence through `battery B to ground G.

Then the rotary magnet was energized for the last digit the privatemagnet relay 134 was also energized, being in multiple with it. Whenthus energized the relay 134 acts as before-to close the private magnetcircuit, and also to change the energizing circuit of the rotarymagnet.The new energizing circuit for the rotary magnet extends from ground Gthrough springs 196 and 197, springs 199 and 201, conductor 208 asbefore, through springs 209 and 211, rotary magnet 132, eontact'point216, side switch wiper 140 to the battery lead 157. Thus, while theimpulses are being delivered, the private magnet relay 134, being slowacting, remains inf an operated position. But as soon'as th impulses aredelivered the relay 134 denergizes. As previously assumed, it the firsttrunk is idle the private magnet 135 will be denergized by the operationof the private magnet relay ;l but if `the trunk is busy, as assumed inthis instance, the private relay 146 is energized. This relay closes theAcircut of the private magnet 135 before the latter has been denergizedby the opening of its circuit at the relay 134. Therefore,

the last busy trunk line.

the private magnet continues in an energized condition until thc privatewiper relay is deenergized, and it in turn is not denergized until theprivate wiper is rotated onto a non-grounded contact point. lVhen theprivate magnet relay 134 dcinergizes and the private magnet 135 is stillheld energized, a new energizing circuit is closed through the rotarymagnet 132 and its interruptcr springs 249'. This circuit extends tromground G13 through the interrupter springs 249, private magnet springs250 and 251, private magnet relay springs 210 and 20S), through thewinding ot' the rotary magnet 132, contact point 216, side switch wiper14() to the battery lead 157thence through battery B to ground G. Therotary magnet 132 now continues to rotate automatically and carry theshaft wipers 125, 126 and 127 past As soon as the private wiper 127engages the contact point upon which there is no guarding potential, theenergizing circuit through the private wiper relay 146 is broken,whereby the springs 247 and 248 disengage and in turn break thecncrgizingcircuit for the private magnet 135, which now permits the sideswitch wipers tov pass from second to third position. In this manner theconnector switch automatically rotates to select an idle trunk line outof the group leading to` the desired oiice. It', however, all of thetrunk lines allotted to the desired office arel busy. the shaft wipersare automatically rotated to the contact points 252, 253 and 254. 100 Itwill be noted that the private contact 254 is insulated or cut ofi' fromthe corresponding private contacts in the other rotary connector banks,so that, when the Wiper 127, reaches this Contact, the 146 isdeinergized, which in turn denergizes the private magnet 135, which inturn opens the rotary magnet circuit permanently and releases the, sideswitch to third position. When the side switch, wipers pass to their 11orespective third positions, an energizing circuit is closed through therelays 141 and 154. This circuit extends from ground (l17 through thebusy relay154, bank contact 252, shaft wiper 125, contact point 227,side 115 switch wiper 136,` ringer relay springs 226 and 244, throughthe winding 142 of the back bridge relay to the battery lead, thencethrough battery B to ground G. The relay 141 thereupon energizes andopens the ringer 120 magnet circuit, whichwas closed for an in stantwhen the side switch passed to third position. The relay 154, uponenergizing, presses the springs 153 and 255 into Contact, whereby thebusy-signaling apparatus I is 125 connected with the rotary shaft wiper126, and a busy-signaling current is sent to the calling subscriber inthe usual manner. The release of the central oflice switching apparatusis brought about when the calling subv 130 private wiper relay wherebyIthe energizing scriber restores the receiver 2 to the switch lhook 3,whereby the spring 17 is pressed out 'and 200 to the release magnet 133,normal springs v1551 and 132 andto the battery lead 157, thence throughbattery ll to ground G. The release magnety 133, upon energizing,operates in the usual manner to restore the connector switch shaft andside switch'to normal position. Vhen the switch shaftl returns to normalposition the normal arm 256 carries the normal spring 1311out ofengagement with the normal spring 132".

whereby the energizing circuit through ,the release magnet 13S isbroken. Also. when the relay 128 deenergizes, the ground potential atthe trunk conductor 191 is removed. and in turn the energizing circuitthrough the release relays 121 and 112 of the selector switches E and Dis broken. YThese relays return to normal position and in turn close anenergizing circuit through their respective release magnets. Theenergizing circuit through the release magnet 121 ot the selector switchE extendsV from ground (lT through the springs 171 and 175,'springs 177and 178, through the release magnet 121. normal springs Q57 and 258 tothe battery lead 157. thence through battery B to ground G. The releasemagnet thereupon energizes and attracts its armature, whereby the shaftwipers and side switch are restored to normal position in the samemanner as in the. connector switch: also,when the switchshatt returns tonormal "position the normal arni 256 carries the normal spring `257 outot engageipent with the Contact point Q56.

Y circuit through the release magnet 121 becomes broken. The circuitthrou'gli the release magnet 10S of the selector switch l) extends fromground G" `through the springs 161 and 166. release relay springs 163and 164.' through the re lease magnet 106. normal springs 110 and 111 tothe battery lead 157. thence through battery B to ground (l. rTherelease magnet 10Sthcieupon energizes and attracts its armature. wherebythe switch Ashatt and side switch are also restored to normal position.As in the preceding switches. the normal arm 10) separatesthe normalsprings 1.1().and 111, whereby the energizing circuit through therelease magnet 16S becomes broken.

Furthermore. when the release relay112 deenergizes and permits thespring 165% to engage the spring 16%, an energizing circuit ,isestablished through the back-release rein position to be released uponthe subi sequent deiinergization of said magnet. The

back-release relay 113, upon energizing. disengages the springs 260 and61, whereby the energizing circuit through the release,

magnet. 21 is broken, thus permitting the line v switch C to return tonormal position.

In the foregoing itv has been shown how selector switches l) and E andthe rotary connector switch F, operates to establish connectioii with adesired lino. 1ty will now be shown how the central ottico selectorswitches y and connector switch L operate to establish a ldesiredconnection with one of the group of lines on the tenth level. Since ithas been assumed that the connector L is connected to the fourth levelot the second selector banks, the number ofthe tirst group of linesending in the tenth level ot said connector L will be 2401. ln callingthe number '21.01 the operation of the lino switch C, master switch J,tirst selector D and second selector l@ is exactly the same as when#2221. was lalled. except that the second selector E receives `tourimpulses instead ot' two and thus selects an idle connector L 4insteadot F. Vihcn the connection is thus exteiidedto the connector L the linerelay 276 and release relay 282 are energized in the. manner explainedfor the relays'lZS and 133 of the connector l". When the calling deviceat substation A is operated for the third digit 0 the impulse springsare t'orced out ot` engageii'ient ten times in the usual manner, thusopening the energizing circuit of the line relay 270 ten times. Eachtime-the rclay Q7() denergizes, the spring engages spring whereby anenergizing circuit is closed extending from ground G throughsprings-.263 and 285, Q87 and '266. private magnet relay "286.

'vertical,magnet 268 and las side switch wiper i272 to battery. Thevertical magnet `266 receives ten impulsesy over the circuitjust tracedand operates to raise the wipers '265. '266 and 267 to a positionopposite-thc tenth bank level. As soon as the switch shaft is raised therst step the arm 289. which is attached to said shaft, permits theotlnormal springs 290 and 291 to enl gage. whereby the release magnetQ77 is connected with the battery B. Before the switch shaft reaches theupper limit of its travel,-that is, with the Wipers 265, 266, and 267standing opposite the tenth levl, the arm 289 forces the springs 292 and2'93 out of engagement with the springs 294 and 295, respectively, andforces spring 293 into engagement with spring 296. The separation ofsprings 292 and 294 disconnects the private magnet relay spring 2962lfrom the private magnet spring 297 which form part of a locking circuitfor the relay 298 when a busy line is called on any of the'first ninelevels. 'The shifting of spring 293 shifts the connection of the contactpoint 299 of the sideswitch Wiper 273, to the relay 278. The privatemagnet relay 288, which is included in the circuit of the verticalmagnet 268, energizes upon the first impulse t0 that magnet and, beingslow-acting, remains in its operated position until after the lastimpulse. When the private magnet relay 288 energizes, it closes anenergizing circuit extending from ground G1 through springs 300 and 301and private magnet 276 to battery. After the last impulse to thevertical magnet the private magnet relay 288 deenergizes and opens theenergizing circuit of the private magnet 27 6, whereupon the saidprivate magnet denergizes and permits the side switch to pass to secondposition. lfVhen the side switch wiper 272 passes from first? to secondposition it shifts the battery connection from the vertical magnet tothe rotary magnet 269. Vhen the calling device is operated for the lastdigit 1) the line relay 270 is4 deenergized once in the usual manner,and operates to close an energizing circuit through the rotary magnet269. This energizing circuit extends from ground G18 through springs 283and 285, 286 and 287, relay 288, springs 302 and 303, and through therotary magnet 269 to battery B. The rotary magnet responds to thisimpulse to rotate the shaft wipers onto the first set-of contacts of thetenth level. The private magnet relay 288 is also energized by thisimpulse and again closes the energizing circuit of the p'rivate magnet27 6. When the private magnet relay denergizes after this impulse to therotary magnet, it opens the circuit of the private magnet 276, whichthereupon' denergizes, if the first line is idle, and permits the sideswitch to pass to third position, thus completing the connection. If,however, the first line of the group #2401 is busy, there will be aguarding ground potential on the private bank contact 304, and when thewiper 266 strikes this grounded contact a locking circuit is closedthrough the private rmagnet 276, independently of the relay 288.

This locking circuit extends from ground ythrough some otherI occupyingswitch (not shown) `to the private bank contact I thence through privatewipeu 266, relay springs 307 and 308, side switch wiper 273, contactpoint 299, springs 293 and 296, relay 278, and private magnet 276 tobattery B. The private magnet thus remains energized and the side switchlocked in second position as long as the-wipers remain on the first busybank contacts, even though the private magnet relay 288Adenergizes.shortlyafter the first impulse to the rotary magnet. Therelay 278, which was 'included in the locking circuit just tracedthrough private magnet, energizes and' forces the spring 309 intoengagement with spring 310. The engagement of springs 309 and 310completes a. connection between the interrupter 279 and rotary magnet269. The rotary magnet then re ceives one impulse .from the interrupter279. and advances the shaft wipers to the` second line of the group#2401. If this second line is also busy, the private wiper 266 findsanother grounded contact, and maintains the energizing circuit of therelay 278 and the private magnet 276, whereupon the rotary magnet willreceive another impulse to cause it to rotate the wipers another step.This automatic rotation of the wipers will continue until an-idle lineis reached, or, in case all the lines of the group are busy, the wiperswill be rotated onto the contacts 311, 312 and 313. The private wiper,finding no ground at contact 313, will permit the relay 278 and privatemagnet 276 to denergize. r1`he denergization of the relay 278disconnects the interrupter 279 from the rotary magnet 269, and thedenergization of the private magnet permitsthe side switch to pass tothird position, whereupon the calling subscriber will receive thebusy-signal in -the manner explained with reference to the connector F.It has been assumed here, however, that the second line of the group isidle. In this case, when the private wiper 266 passes from the contact304 the relay 278 and private magnet 276 are denergized. rl`hedeinergization of the relay 278 disconnects the interrupter from therotary magnet, as before explained, and the private magnet allows theside switch to pass to third position. 1Vhen the side switch of theconnector L passes to third position the connection is completed to thecalled substation and the bells are rung in the manner explained inconnection with the connector F'. Also, in this instance, as in theprevious one, the removal of the receiver at the called substationcauses the energization of the backbridge relay, which opens the circuitof the ringer relay 315. The energization of the back-bridge relay 314also opens the short: circuit around the resistance 332 by separatingthe springs 321 and 322, thus including thisresistance in theholdingcircuit of the release relays 112, 124 and 282 of the switches neoted toone of the first nine levels of the connector L, as, for instance,#24:41, the operation of the central'oiice switching mecha nism is thesame for the irst three digits as thatexplained in the preceding case,with theexeeption that the switch shaft is raised only four steps, andconsequently the springs 292 and 293 are not operated by the arm 289.

When the calling device is operated for the last digit the rotary magnet269 receives one impulse, rotates the Wipers onto the first contact, andif the called line is idle the side switch is tripped to third position,in the manner explained when it was assumed that the first line of thegroup 2401 was idle. If', however, the line 2441 is busy when called,the Wipers are not automatically rotated to the next contacts, butremain in engagement With the line #2441, and the side svvi-tch islocked in second position, thus preventing the completion of theconnection to the busy, line, and giving the callinef subscriber thebusy-signal. The manner in Which the side switch is locked when a busyline is encountered is as follows: /Vhenever a. line is 'i busy theprivate connector bank contacts AWith spring viously traced,

of that line are provided with a guarding ground potential. Thus, whenthe Wipers are rotated to a busy line, and since the side switch is insecond position, this ground potential is extended fronrthe private`bank contact over wiper 266, relay springs 307 and 308, side switchWiper 273, contact point 299,

springs 293 and 295, side switch Wiper 275,

ringer relay springs 316 and 317 and Winding 818 of' back-bridge relay3H to the bat-V tery B. The relay 314: thereupon energizes and 'byforcing spring 320 into engagement 319 closes a locking circuit throughtheprivate magnet 276. This locking circuit extends from the groundedprivate bank' contact to the spring 295, as preand thence through y'thesprings 319 and 320 and private magnet 276 to battery. This lockingcircuit for the private magnet is established as soon as the wiper reachthe busy line, and before the private magnet relay 288 has -time todenerf gize. The relay 288 denergizes inthe usual manner after tlie lastrotary impulse, and as the private magnet now remains energized aenergizing, shifts the spring 308 out of engagement with spring 307 andinto engagement with the spring 525, whereby the lockf 'ing ground oftherelav 314 and private magnet 276is transferred from the private bankcontact to ground G20; This shifting of the locking ground is for thepurpose of maining the rotary magnet 269 from the impulsespring 285, sothat the said magnetwvill not be energized when the receiver at thecalling substation is restored to the switch hook.

While the private magnet 27 6 .is thus. energizedit locks the sideswitch in second position to prevent the completion of the con-- thebusy-signaling machine I with the calling'line by Way of the springs 327and 328,-

side switch Wiper 27st and condenser 2,81. VWhen a busy line has beencalled, the connectorL and selectors D and E are released nection withthe busy line, and also connects by the restoration of the receiver tothe switch hook in the same manner connector F was released.

In the description of the operation of the connector F it was explainedhow the .group of trunk lines corresponding to number 2221 mightcomprise three trunks, the `fourth set of bank contacts reserved forgiving the busy signal in case all three trunksy are busy. Vith thisarrangement thnext group of trunks in the second level would be reachedby calling the number 2225. The five impulses for the digit 5 wouldcause the connector Wipers to be rotated five steps over the threetrunks and the blank set of contactsy of the first in thelsecond levelbeingy that the group to the first trunk of the second group.

If this trunk is busy the Wipers then begin ,to advance automatically-to find an idle trunk in the group after the last impulse from thesubstation is delivered. Thus it is evident that each bank level ofthese connectors may accommodate more than one group of lines. the firstidle line of any group being accessible by calling the numbercorresponding to the position of the bank contacts of the first line inthe group. Likewise, in the Connector L each level in which theautomatic rotaryvfeature is provided may accommodate more than a singlegroup of trunk lines. In the case assumed herein the next group in thetenth level would be numbered M05.' Y f IFrom the foregoing it will beseen that I provide rotary connectors, F and L, for example. which arecontrollable over metallic line circuits. In this way these rotaryconnectors are controllable without the necessity of grounding the linesat the substations. Heretofore all rotary connectors, so tar as I am nowaware, have been controlled by grounding lthe line at the. callingsubstation, or at the operators position. depending upon g,he charm-.terof the system, lilith in v im- .mshing talking current over thesubscribers lines to the substations thereof. For some of the broaderpurposes of my invention, however, the common battery feature 1s notnecessary, and the first selectors may be given other arrangements. Asillustrated, the rotary connector F is rotary in all levels thereof, sothat if all of the trunk lines of any particular group are busy thecalling `trunk lines are connected subscriber will automatically receivethe busy-signal in the manner explained. The rotary connector L,however, is of such character that it may bel rotary in one or morelevels, and then operate like an ordinary connector in the other levelor levels. The wipers of either of the connectors F or L may be rotatedto any desired contact'in their respective bank levels by impulses fromthe calling stationfthe automatic rotation taking )lace only after thelast impulse has been delivered. .This cnnector L is, therefore,equipped with a discriminating busytest apparatusthat is to say,v abusy-test apparatus which willdiscriminate between busy trunk lines andbusy single telephone lines. By this I mean that the busy test is of adiscriminating nature, inasmuch as when a trunk ,line tests busy theconnector does one thing and when a single subscribers line tests busythe connector does scriber recelves. the busy-signal.` When a singlesubscribers line tests busy this same connector then remains locked onthat line, .and the calling subscriber receives the busy,- signal-thatis, assuming, of course, that the single subscribers lines are connectedto the bank levels upon which the connector L operates as an ordinaryconnector, and that the which the switch acts as a rotary connector, ashas been previously pointed out. Thus 0- the connector is capable ofdiscriminating 6 between busy trunk lines and busy single lines,operating in one Way when it finds a busy trunk line. and operating inquite a different way whcn it encounters a busy Single liuc. This, asexplained, is all accomplished in a svstcm in which the switches areconto the levels upon' trolled over metallic line circuits. In this wayrotary connectors are controlled and operated without the necessity ofgrounding the line at the calling substation.

vWhat I claim as my invention is zl. In a. telephone exchan e system,the combination with subscribers telephones, a line individual to eachtelephone, a line` switching device having line terminals and a group oftrunk terminals, of a moving contact member for said switching device,automatic means for stepping said member to any of said line terminalsor the first trunk terminal of said group, means actuated in case saidfirst trunk is busy for steppingusaid 80 member to a terminal of an idletrunk line, said switching device operated over a circuit including bothsides of any one of said lines in series, said circuit passing throughthe subscribers telephone instrument.

2. In a telephone exchange system, the combination .with a telephoneline extending from a substation to a central oHice individual to asubscriber, of a connecting circuit at the central ofiice, aprogressively vmovable connect-ion -switch for uniting said connectingcircuit with the` telephone line, a line switching device havingterminals of lines in the exchange, trunk lines leading to terminals ofsaid device, a contact.arna for said device adapted to sweep over saidterminals to unite said connecting circuit with said terminals,automatically operated mechanism for advancing said arm over saidterminals and over sald trunk terminals until an idle trunk line isreached, a busy Signal, means actuated in :ase all of said trunk linesare busy for applying said busysignal to said connecting'cincuit,a-relay individual to said device, said relay energized over both sidesof said line in series for operating said switching device, a receiverswitch hook vat said telephone, said relay circuit controlled thereby.

In a telephone system, a calling subscribers telephone, aline individualthereto, the 'combination of a plu 'ality of telephone lines running tothe same'substation, telephones on said lines, an automatic switchprovided with means for extending connection from said calling line toany one of said telephone lines, automatic means 'for causing theoperation of said switch to select the first idle one of said lines, acommon batter relays allotted to said switch and controlling 2 the flowot talking current from said battery to the called telephone line, and acircuit over which the said switching means is controlled comprising thetwo sides of said subscribers line circuit in s'eries.

4. In a telephone system, a calling subscribers telephone, a lineindividual thereto, a plurality ot' lines any one of which will servethe purpose of a calling subscriber, means including an automatic switchcommon toa plurality of said lines forfautomatically selecting an idleline for the caling subscriber, means controlled at said automaticswitch for supplyingf all the talking curient'to a' subscriberssubstation, and a metallic line circuitp'ver which the said` arrela'yindividual thereto through the me- 'dium o'which said substation controlis eX- .,ercised, said-relay energized over both corr" .25 .ductors inany one of said telephone lines in f'series, said relay circuitincluding a Vswitch l iitthe telephone' directly operated by the/rsivitch hook.

l arl 6. In a telephone system, a connector, a

"relay, trunklv lines leading from said connec- 'tor, t2-callingsubstation, a line circuit indi- Y 'vidual thereto, means fortransmitting cur- .'rent over two/sides of said line circuit in seriestosaid relay to operate said connector Slin accordance with the last twodigitsof the,

called n iimber, a receiver switch hook, a switch at said telephonedirectly controlled Vby said hook, said switch included in the cirf,cuit of said relay, said connector provided l0 lwith means forautomaticaly selecting an idle trunk line, and means for transmitting la busy-signal over said line circuit if all 'the ,f trunk lines arebusy.

i 7 vIn arch-,phone system, a telephone station, a lin'e circuitindividual thereto, means for transmitting calling current over the twosideis-osaidI circuit in series, a connector responsive to' saidcurrent, lines leading from ",said connector, means whereby when theconnector finds one of said lines busy it auto- .,natically passes tothe-next line, and means whereby when the connector inds another linebusy it may stop and go no farther, a reilay for operating saidconnector, a receiver 1I-switch hook, a switch at said stationoperater'llby said hook, said switch included in the`-circuit of saidrelay.

I n a telephone system, a telepho-ne station, aline circuit individualthereto, means 30' for transmitting current over said circuit, a bankof" contacts, lines leading from said contacts;l a wiper adapted toengage sai contactsy' mechanism for actuating said wiper, a relayoperated over two sides of said Se circuit in series for operatingsaid'mechanism, means for preventing` said wiper from passing a busycalled line, and means Jfor causing said wiper to automatically selectan idle line, a receiver switch hook, a switch at said station operatedby said hook, said switch included in the circuit of said relay.

9. In a telephone system, a `telephone station, a line circuitindividual thereto, a stepby-step mechanism, a plurality of linesdivided into two groups, meansincluding a relay whereby said mechanismis operated over two sides of said line circuit in series to select acertain called line .from one group whether idlev or busy, and meanswhereby said mechanism is operative to automatically select an idle oneof the lines in the other group, areceiver switch hook, a' switch atsaid station operated by4 said hook, the circuit of said relay includingsaid switch. f 85 10.` In a telephonesystem, a telephone station, a linecircuit individual thereto, tele'- phone lines, other lines, switchingmeans including a relay responsive to current sent over two sides ofsaid line circuitin series Q0 for testing the lines, means forcausingfone kind of operation of said switching-means when atelephoneline tests busy, and means for causing another kind ofoperation when one of said other lines tests busy, a receiver switchhook, a switch at said station operated by said hook, said switchincluded in the circuit of said relay.

11. In a telephone system, a telephone station, a line circuitindividual thereto, a connector having a relay operated over two sidesof said line circuit in series, said connector having a plurality'ofparallel planes of operation, means whereby said connector isautomatically operative in o'iieor more 105; of said planes toautomatically select anV idle line, and means whereby said connector isoperative under substation control in one'or more of the planes, areceiver switch hook, a switch at said station operated by v11`0 saidhook, said switch included in the circuit of said relay.

12. Ina telephone system, suitable lines, a telephone station, a linecircuit individual thereto, a connector having a plurality of parallelplanes of operation under manual control, and means whereby saidconnector is operative automatically in one of said planes toautomatically select an idle line,

a relay operable over two sides of said line circuit in series foroperating said connector, a receiver switch hook, a switch at saidstationA operated by said hook, said relay` included in the circuit ofsaidl switch.

13. In a telephone system, telephone lilies, 4125 trunk lines, aconnector, a telephone station,

d a line circuit individual thereto, a relay roil operating saidconnector, means'for transmitting calling current overtwo sides of saidcircuit in series to said relay to operate automatically said connector,said connector having mechanism operative under substation control tofind a called telephone line, means whereby said connector is operativeto automatically select an idle trunk line, means for insuring abusy-signal if the called telephone line is usy, means for insuring alike signal if' all the trunk lines are busy, a receiver switch hook,aswitch at said station operated by said hook, said relay included inthe circuit of said switch, means including first selec tois forreaching said connector, and means for automatically' selecting idlefirst selectors, said selectors controllable over the said metalliccircuit in accordance with the first digit of" the called number.

In a telephone system, a connector, a relay, trunk lines leading fromsaid connector, a telephone station, a line ciicuit individual thereto,means for transmit-ting current over two sides of said circuit in se-vries to said relay to operate said connector in accordance with the lasttwo digits of the called number, said connector provided with means forautomatically selecting an idle trunk line, means f'or transmitting abusysignal over said metallic circuit if all the trunk lines are busy, areceiver switch hoo-k, a switch at said station operated by said hook,said relay included in the circuit of said switch, means including firstselectors for reaching said connector, andineans for lautomaticallyselecting idle first selectors,

said selectors controllable over the two sides of said line circuit inaccordance with the first digit of the called number.

15. In a telephone system, a telephone station, a line circuitindividual thereto, means for transmitting calling current over twosides of said circuit in series, a connector having a relay responsiveto said current, lines leading from said connector` means whereby whenthe connector finds one of said lines busy it automatically passes tothe next line, means whereby when the connector `finds another line busyit may stop and go no farther, a receiver switch hook, a switch at saidstation operated by said hook, said relay included in thev circuit ofsaid switch, means including first selectors for reaching saidconnector, and means for selecting idle first selectors, said selectorscontrollable over the two sides of said line circuit in accordance withthe first digit of the called number.

16. In a telephone system, a circuit individual thereto` an line. aliiic automatic switch opeiative o'vcr two sides oi said line circuit'inseries in accordance with the last digits of" the called number, one ormore grounded private bank contacts and a non-v grounded private bankcontact for said switch for controlling said switch. means under thccontrol of a subscriber for moving said switch over certain of saidgroundl grounded contacts.

ed contacts, and means for automatically moving said switch over otherof said 17. Ina telephone system, a line, a line circuit individualthereto, an automatic switch, a rotary magnet therefor controlled overtwo sides of said line circuit in series in accordance with the lastdigit of the called number, a plurality of grounded and non-groundedbank contacts for controlling said operation, and means for energizingsaid rotary magnet when connection is made with a grounded contact ofsaid bank.

1S. In a telephone exchange system, the combination with a lineswitching device having' line terminals and a group of trunk terminals,of a moving contact member for said switching device, automatic meansincludinga relay for stepping said member to any of said line terminalsor the first trunk terminal of' said group, means actuated in case saidfirst trunk is busy for stepping said member to a terminal of an idletrunk line, a line circuit over two sides'in Series of which the saidswitching device is `operated,van il means at the central stationincluding said relay for supplying talking current over said circuit.

19. In a telephone exchange system, the combination with a telephoneline extending from a sub-station to a central office, of a connectingcircuit at the central office, a connection switch for uniting saidconnecting circuit with the telephone line, a line switching devicehaving terminals for lines in the exchange, a relay for operating saiddevice, trunk lines leading to terminals of said device, a contact armfor said device adapted to sweep over said terminals to imite saidconnecting circuit with said terminals, automatically operated mechanismfor advancing said arm over said line terminals and for' automaticallyadvancing said arm over said trunk terminals until an idle trunk line isreached, a busy signal, means actuated in case all of said trunk linesare busy ,for applyingsaid busy-signal to said connecting circuit, aline circuit over two sidesin series of which the said .relayisoperated, and means at the central

